PUEBLO, Colo. (AP) — Police believe three girls who accidentally drowned in a southern Colorado swimming pool last week jumped into the deep end.

Pueblo police Sgt. Eric Gonzales said Tuesday that a nearby adult heard the young sisters and their teenage babysitter jump into the 8-foot-deep section of a pool at a mobile home park.

He said that an unidentified adult soon saw one of them floating in the water and notified staffers, who tried to save the girls before police arrived.

Other children were in the pool at the time. There was no lifeguard.

Initial autopsies showed that 17-year-old Joo Hyun Lee, 6-year-old Amaya Gandarilla and her 3-year-old sister Azucena accidentally drowned Aug. 8.

Final autopsy reports will be released in about a month following toxicology tests.